Biology subjects

Pollmann, S.

Publications and source records attributed to Pollmann, S..

7 recordsLinked to original sources

bioRxiv2018

Cross-task perceptual learning of object recognition in simulated retinal implant perception

The perception gained by retina implants (RI) is limited, which asks for a learning regime to improve patients visual perception. Here we simulated RI vision and investigated if object recognition in RI patients can be improved and maintained through training. Importantly, we asked if the trained object recognition can be generalized to a new task context, and to new viewpoints of the trained objects. For this purpose, we adopted two training tasks, a naming task where participants had to choose the correct label out of other distracting labels for the presented object, and a discrimination task where participants had to choose the correct object out of other distracting objects to match the presented label. Our results showed that, despite of the task order, recognition performance was improved in both tasks and lasted at least for a week. The improved object recognition, however, can be transferred only from the naming task to the discrimination task but not vice versa. Additionally, the trained object recognition can be transferred to new viewpoints of the trained objects only in the naming task but not in the discrimination task. Training with the naming task is therefore recommended for RI patients to achieve persistent and flexible visual perception.

neuroscience↗

bioRxiv2018

Not scene learning, but attentional processing is superior in team sport athletes and action video game players

We tested if high-level athletes or action video game players have superior context learning skills. Incidental context learning was tested in a spatial contextual cueing paradigm. We found comparable contextual cueing of visual search in repeated displays in high-level amateur handball players, dedicated action video game players and normal controls. In contrast, both handball players and action video game players showed faster search than controls, measured as search time per display item, independent of display repetition. Thus, our data do not indicate superior context learning skills in athletes or action video game players. Rather, both groups showed more efficient visual search in abstract displays that were not related to sport-specific situations.

neuroscience↗

bioRxiv2018

The effect of acquisition resolution on orientation decoding from V1: comparison of 3T and 7T

Previously published results indicate that the accuracy of decoding visual orientation from 7T fMRI data of V1 peaks at spatial acquisition resolutions that are routinely accessible with more conventional 3T scanners. This study directly compares the decoding performance between a 3T and a 7T dataset that were acquired using the same stimulation paradigm by applying an identical analysis procedure. The results indicate that decoding models built on 3T data are comparatively impaired. Moreover, we found no evidence for a strong coupling of BOLD signal change magnitude or temporal signal to noise ratio (tSNR) with decoding performance. Direct enhancement of tSNR via multiband fMRI acquisition at the same resolution did not translate into improved decoding performance. Additional voxel selection can boost 3T decoding performance to the 7T level only at a 3mm acquisition resolution. In both datasets the BOLD signal available for orientation decoding is spatially broadband, but, consistent with the size of the BOLD point-spread-function, decoding models at 3T utilize spatially coarser image components.

neuroscience↗

bioRxiv2018

Substrate channeling in oxylipin biosynthesis through a protein complex in the plastid envelope of Arabidopsis thaliana

Oxygenated membrane fatty acid derivatives dubbed oxylipins play important roles in the plants defense against biotic and abiotic cues. Plants challenged by insect pests, for example, synthesize a blend of different defense compounds that, amongst others, comprise volatile aldehydes and jasmonic acid (JA). Because all oxylipins are derived from the same pathway, we asked how their synthesis might be regulated and focused on two closely related, atypical cytochrome P450 enzymes designated CYP74A and CYP74B, i.e., allene oxide synthase (AOS) and hydroperoxide lyase (HPL). Both enzymes compete for the same substrate but give rise to different products. While the final product of the AOS branch is JA, those of the HPL branch comprise volatile aldehydes and alcohols. AOS and HPL are plastid envelope enzymes in Arabidopsis thaliana but accumulate at different locations. Biochemical experiments identified AOS as constituent of complexes also containing lipoxygenase 2 (LOX2) and allene oxide cyclase (AOC), which catalyze consecutive steps in JA precursor biosynthesis, while excluding the concurrent HPL reaction. Based on published X-ray data, the structure of this complex could be modelled and amino acids involved in catalysis and subunit interactions identified. Genetic studies identified the microRNA 319 (miR319)-regulated clade of TCP (TEOSINTE BRANCHED/CYCLOIDEA/PCF) transcription factor genes and CORONATINE INSENSITIVE 1 (COI1) to control JA production through the AOS-LOX2-AOC2 complex. Together, our results define a molecular branch point in oxylipin biosynthesis that allows fine-tuning the plants defense machinery in response to biotic and abiotic stimuli.

cell biology↗

bioRxiv2018

Spatial contextual cueing is not a limiting factor for expert performance in the domain of team sports or action video game playing

We investigated in two experiments if handball and action video game players show improved implicit learning of repeated spatial configurations for efficient search guidance in comparison to a control group without sport or video game proficiency. To this end, we used both a sport-specific pseudo 3-D contextual cueing task and the original contextual cueing paradigm (Chun & Jiang, 1998). Contextual cueing was present in all groups. However, handball and action video game players did not differ in the strength of contextual cueing from the control group. Action video game players had shorter search times than controls in both experiments. In contrast, the handball players searched faster than controls in the sport-specific displays of Experiment 1 but not in the symbolic search task of Experiment 2. Thus, our findings provide no evidence that contextual cueing is a limiting factor for expert performance in the domain of team sports or action video game playing.

neuroscience↗

bioRxiv2017

Tolerance To PVY Infection In Potato Is Conditioned By Perturbation Of Small RNA-Gibberellin Regulatory Network

Potato virus Y is the most economically important potato viral pathogen. We aimed at unraveling the roles of small RNAs (sRNAs) in the complex immune signaling network controlling the establishment of tolerant response of potato cv. Desiree to the virus. We constructed a sRNA regulatory network connecting sRNAs and their targets to link sRNA level responses to physiological processes. We discovered an interesting novel sRNAs-gibberellin regulatory circuit being activated as early as 3 days post inoculation before viral multiplication can be detected. Increased levels of miR167 and phasiRNA931 were reflected in decreased levels of transcripts involved in gibberellin biosynthesis. Moreover, decreased concentration of gibberellin confirmed this regulation. The functional relation between lower activity of gibberellin signaling and reduced disease severity was previously confirmed in Arabidopsis-virus interaction using knockout mutants. We further showed that this regulation is salicylic acid-dependent as the response of sRNA network was attenuated in salicylic acid-depleted transgenic counterpart NahG-Desiree expressing severe disease symptoms. Besides downregulation of gibberellin signaling, regulation of several other parts of sRNA network in tolerant Desiree revealed similarities to responses observed in mutualistic symbiotic interactions. The intertwining of different regulatory networks revealed shows how developmental signaling, disease symptom development and stress signaling can be balanced.

plant biology↗

bioRxiv2016

The effect of acquisition resolution on orientation decoding from V1 BOLD fMRI at 7 Tesla

A decade after it was shown that the orientation of visual grating stimuli can be decoded from human visual cortex activity by means of multivariate pattern classification of BOLD fMRI data, numerous studies have investigated which aspects of neuronal activity are reflected in BOLD response patterns and are accessible for decoding. However, it remains inconclusive what the effect of acquisition resolution on BOLD fMRI decoding analyses is. The present study is the first to provide empirical ultra high-field fMRI data recorded at four spatial resolutions (0.8 mm, 1.4 mm, 2 mm, and 3 mm isotropic voxel size) on this topic -- in order to test hypotheses on the strength and spatial scale of orientation discriminating signals. We present detailed analysis, in line with predictions from previous simulation studies, about how the performance of orientation decoding varies with different acquisition resolutions. Moreover, we also examine different spatial filtering procedures and its effects on orientation decoding. Here we show that higher-resolution scans with subsequent down-sampling or low-pass filtering yield no benefit over scans natively recorded in the corresponding lower resolution regarding decoding accuracy. The orientation-related signal in the BOLD fMRI data is spatially broadband in nature, includes both high spatial frequency components, as well as large-scale biases previously proposed in the literature. Moreover, we found above chance-level contribution from large draining veins to orientation decoding. Acquired raw data were publicly released to facilitate further investigation.

neuroscience↗